The general object of metrology (i.e., the science of measurement) is to monitor a physical phenomenon to permit a record of the monitored event(s). If the potential to record the measured or monitored data is lost, then the entire basic purpose of the metering device and/or effort fails.
The basic function and purpose of metering devices can be applied to a number of contexts. One broad area of measurement relates, for example, to utility meters. These may include the monitoring of consumption of a variety of forms of energy or other commodities, such as electricity, water, gas, and oil, just to name a few.
Intermittent power outages (or other conditions, including brown outs) can occur in even the most well maintained systems. For example, an electrical power system can become damaged due to storm debris (e.g., falling limbs) or high winds, or from an accident (for example, vehicles such as trucks or cars knocking down utility poles and power lines). Under certain load shedding conditions, it may even become necessary for power to a given location to be deliberately interrupted.
Regardless of such relatively routine causes (or possibly other less routine sources) of power outages, an inherent problem is that an electrical measuring device with electrically powered metrology and memory storage registers may lose accumulated data in the event of even a routine power outage. Prior attempts have been made to address the technical problem of saving data at power down in a solid state metering platform.
One known method of addressing the issue of memory integrity during instances of lost power employs a technique or storage algorithm that stores electricity meter quantities to a non-volatile memory whenever a power outage occurs. In such approach, the technique involved the use of what may be relatively complicated and costly power fail detection circuits and power supply hold up components. A relatively significant storage capacitance is required to store the necessary energy increments to complete a non-volatile memory write after a power failure has been detected.
Another known method of addressing such present issues involves saving metered energy values at fixed time or energy intervals. Such approach has been practiced such that if the power fails during the energy write, the integrity of the metered data is not compromised. Such technique provides a relatively lower risk of data loss compared to the power fail detection technique. However, the relative endurance of non-volatile memory devices becomes a concern because most non-volatile memory devices are limited over the life of such a device by the maximum number of times to which an area of memory can be written.
There are other known efficient and affordable non-volatile memory technologies used in many electronics applications, including metrology. Such known technologies include EEPROM (Electronically Erasable Programmable Read Only Memory) and flash memory. An exemplary method of using flash memory for storing metering data is disclosed in U.S. Pat. No. 6,798,353 B1 (Seal et al.). It should be noted that other applications may utilize alternative non-volatile memory structures such as EPROMS, other ROM devices, certain types of RAM, namely battery-backed RAM, or others. The number of times a non-volatile memory device such as EEPROM or flash can be erased and then rewritten is limited over the lifetime of such devices. Such limiting phenomenon is known as memory “endurance”, and is often measured by a limited defined number of “writes”. For example, many conventional EEPROM devices may support about one million writes, while many typical flash structures may support between ten-thousand and one-hundred-thousand writes.
Known references have addressed exemplary procedures and algorithms for increasing memory endurance and integrity. For example, U.S. Pat. No. 6,219,656 B1 (Cain et al.) discloses a technique that alternates saved metering data between two EEPROM locations, thus doubling the endurance of the memory device.
Other arrangements and aspects of memory storage in electronic-based electricity meters are known. See, for example, disclosures set forth in U.S. Pat. Nos. 4,516,218 (Hamilton); 5,477,216 (Lee, Jr. et al.); 6,006,212 (Schleich et al.); 6,374,188 B1 (Hubbard et al.); 6,507,794 B1 (Hubbard et al.); and 6,577,961 B1 (Hubbard et al.).
The disclosures of all of the above-referenced patents are incorporated herein for all purposes by virtue of present reference thereto.
While useful for their purposes, none of the above referenced approaches solve the problems addressed by the presently disclosed technology, namely, the need for a cost-effective, efficient, non-volatile memory structure and associated methodology used to store metering data while also ensuring memory integrity and increasing memory endurance.